Elevated Levels of Mercury in Lake Whatcom Fish -- Identification of Potential Sources and Contributing Factors with Recommendations for Additional Sampling Needed to Determine Sources
Proposal by USGS to Whatcom County Health Department, May 2002
Problem- Lake Whatcom is a large, natural lake located in Whatcom County, Washington near the western edge of the Cascade Range foothills (fig. 1). The surface area of the lake covers about 5,000 acres, and the total watershed area is about 32,000 acres. The lake can be divided into three distinct basins formed by glacial sills. Basins 1 and 2 (fig. 1) are relatively small and shallow (less than about 80 feet). Basin 3, which has a maximum depth of about 330 feet, contains 96 percent of the lake volume. Basin 1 is in the most urbanized part of the watershed, lying largely within the city limits of Bellingham. Several streams drain to the lake, and to maintain optimal lake levels, water is diverted to the lake from the middle fork of the Nooksack River. Protection of lake quality is important because the lake is a source of drinking water for about 86,000 Whatcom County residents, and because it is used extensively for sport fishing, swimming, and other types of recreation.
Concerns about mercury contamination in Lake Whatcom were raised after a survey conducted by the Washington State Department of Ecology (Ecology) in 1998 reported a concentration of 0.5 mg/g (microgram per gram, wet weight) in a composite sample of smallmouth bass fillets (Serdar and others, 1999). For comparison, the national average concentration of mercury in sport fish fillets is 0.36 mg/g, and for smallmouth bass it is 0.34 mg/g (U.S. Environmental Protection Agency, 1992). Serdar and others (1999) also sampled bottom sediments from Lake Whatcom, and they reported that the highest concentration of mercury in samples was 0.46 mg/g (dry weight). For reference, concentrations of mercury in the silt-clay fraction of bed sediments sampled from streams located in forest and reference areas in Puget Sound Basin ranged from 0.07 to 0.34mg/g (median 0.1 mg/g) (MacCoy and Black, 1998).
To address concerns about possible mercury contamination in Lake Whatcom, Ecology, Washington State Department of Health, Washington Department of Fish and Wildlife, and Whatcom County Health and Human Services Department conducted a second study in 2000. The goal of the second study was to help determine if consumers of Lake Whatcom fish were at risk from mercury exposure. During this study, 273 samples of finfish and signal crayfish were collected from Lake Whatcom and analyzed to determine concentrations of mercury and other constituents (Serdar and others, 2001).
The second study confirmed that mercury concentrations in smallmouth bass from Lake Whatcom are elevated relative to the national average concentration of 0.34 mg/g. The average concentration was 0.49 mg/g, and the maximum concentration was 1.84 mg/g. Results from the second study also raised interesting questions because concentrations in some fish tissue samples from basin 3 were elevated relative to those in basins 1 and 2. This result was somewhat unexpected because basin 3 is large and the contributing drainage area to basin 3 has a smaller percentage of urban land use than basin 1. The reasons that concentrations were higher in basin 3 were not determined, but Serdar and others (2001) conjectured that transport of mercury to the lake from tributaries or diversions, or processes that convert mercury to methylmercury in the lake or in connected wetlands might be contributing factors. In fact, bottom sediments of lakes in urban areas tend to have higher concentrations of total mercury, but lower concentrations of methylmercury, because urban land-use practices tend to disrupt the ecosystems that most readily convert inorganic mercury to methylmercury (David Krabbenhoft, U.S. Geological Survey, written commun., April 2002).
Comments and critique:
"....and to maintain optimal lake levels, water is diverted to the lake from the middle fork of the Nooksack River. ...."
Water is diverted to supply the Georgia Pacific West industrial facility on the Bay.
"....Protection of lake quality is important because the lake is a source of drinking water for ...."
The lake is the sole source of drinking water for ...."
Some of the possible sources of mercury in Lake Whatcom are atmospheric deposition from global and local sources, discharges from tributaries (including the diversion from the Nooksack River), landfills, dumpsites, and local mining operations. Of these possible sources, local interest has focused on a chloralkali plant that operated in the city of Bellingham and discharged mercury to the atmosphere from early 1960s until the late 1990s. A major element of this study will be to assess the importance of this source.
Objectives- The objectives of this study are to:
Relevance and Benefits- This study will address the second long-term goal of the USGS 2000-2005 Strategic Plan to maintain, provide and improve long-term environmental and natural resources information, systematic analyses and investigations, and predictive tools for scenario building and decision making about natural systems. Conducting a basin-wide assessment of the source and transport of a contaminant is one of the major goals of the Washington District Science Plan. The study serves a local need to develop a better understanding of the relation between sources, processes, and concentrations of mercury in Lake Whatcom.
Approach- The success of this study relies on the acquisition, synthesis, and analysis of available data and information, not all of which are found in published reports or in reports that are not readily available. Because of their knowledge of the data and information, Whatcom County Health Department will assist the USGS in obtaining them. The USGS will compile a reference list of all information and materials gathered and return them to the Whatcom County Health Department on completion of the study.
Additional data will become available from two studies that are in progress and a study planned for summer 2002. The two studies in progress are being conducted separately by the Whatcom County Health Department and Ecology and will provide data on concentrations of mercury in 55 samples of fish tissue from other lakes in Whatcom County. An attempt will be made to use these data to help determine the effects local and regional sources of mercury, but high variability in concentrations of mercury in adult sport fish may make it difficult to establish a relation between atmospheric deposition of mercury and mercury in fish (David Krabbenhoft, U.S. Geological Survey, written commun., April 2002).
The planned study, to be conducted by Ecology, will provide data on concentrations of mercury in 30 sediment samples and three sediment cores collected from Lake Whatcom and in bed sediment samples collected from some streams draining to the lake. In addition, Ecology plans to add total mercury to the list of analytical determinations for samples that will be collected quarterly from 10 tributaries to Lake Whatcom as part of the dissolved oxygen TMDL study. This study will coordinate with the Ecology study to collect and analyze sediment cores from five other nearby lakes. Details are provided in the following paragraphs.
"....local interest has focused on a chloralkali plant that operated in the city of Bellingham and discharged mercury to the atmosphere ...."
Grossly inadequate characterization, the plant should be named, Say:
"the Georgia Pacific West industrial facility on the Bay" , and it discharged mercury to THE BAY AND the atmosphere
"....and return them to the Whatcom County Health Department on completion of the study....."
The raw-data bibliography info should not be controversial, will contribute to everyone's understanding of the information and circumstance, and should be made public as soon as collected, not held to the end.
Approach for Objective 1
This objective will be addressed by determining spatial variations in concentrations of mercury in Lake Whatcom using data from the 30 surface sediment samples that will be collected and analyzed by the Washington State Department of Ecology in summer 2002, and comparing spatial variations in concentrations with 1) the existing inventory of known and potential sources of mercury; 2) locations of tributaries discharging to the lake; 3) land use adjacent to the lake and in watersheds draining to the lake; 4) available information about the natural abundance of mercury in geologic materials in the Lake Whatcom watershed and in the area draining to the middle fork of the Nooksack River; and 5) concentrations of mercury in streambed sediments that will be collected and analyzed during Ecology's study. The 30 sediment samples also will be analyzed to determine grain-size distribution and concentration of total organic carbon, and they will be archived for possible future use.
Approach for Objective 2
This objective will be addressed by collecting five cores, one from each of five nearby lakes, in addition to the three cores Ecology plans to collect from Lake Whatcom. The five nearby lakes selected for coring will be located both upwind and downwind from the chloralkali plant, but final selection will depend on the review of data and information to be conducted during the first part of this study. Ten horizons from each of the eight core samples will be analyzed for total mercury, total lead, lead-210, and total organic carbon. To help resolve any questions about dating the horizons using the lead-210 data, five horizons from each core also will be analyzed for cesium-137. Variations in concentrations of total lead also can help with dating the core horizons. In graphing data collected as part of the USGS reconstructed trends study, Yake (2001) observed that lead concentrations in Lake Ballinger in the Seattle area peaked just after leaded gasoline was banned from use in new cars in 1975.
Data from analysis of the core samples will provide information on mercury accumulation rates in Lake Whatcom and other local lakes. These data will help determine 1) if the rates of mercury accumulation in Lake Whatcom and other local lakes are higher than what can be attributed to global cycling of mercury, 2) if the rates are higher than those in other lakes that have been sampled in Washington State, and 3) if accumulation rates of mercury in the local lakes are different.
Data on accumulation rates of mercury in lakes due to global cycling are available from scientists in the USGS Mercury Studies Program (for a description of the USGS role in mercury studies see Krabbenhoft and Rickert, 1995) and other scientists (Engstrom and Swain, 1997, for example). The USGS reconstructed trends study sampled Lake Washington, Lake Ballinger in Seattle, and the Tolt Reservoir in the central Cascade Range of Washington State. Variations in accumulation rates in the lakes sampled during this study will be used along with available wind-direction data to infer the effects of known local and regional sources of airborne mercury.
Approach for Objective 3
The ongoing studies conducted by the Whatcom County Health Department and Washington State Department of Ecology will provide new data on concentrations of mercury in 55 samples of fish tissue from other lakes in Whatcom County. Controlling for species, age, and size, these data will used in conjunction with other available data on concentrations of mercury in tissue of fish from Lake Whatcom to try and infer the effects of known local and regional sources of mercury.
Approach for Objective 4
Approaches to objectives 1 and 3 are based on finding spatial relations between concentrations of mercury sediment and fish tissue samples and potential sources of mercury. Previous attempts to isolate the effects of mercury loading on mercury levels in fish have been confounded by environmental factors that affect the speciation of mercury. For example, conversion of inorganic mercury to methylmercury in the deep, possibly anoxic sediments of basin 3 might be a factor contributing to the elevated levels of mercury in fish tissue from basin 3 relative to basins 1 and 2. As a first step in addressing this issue, five of the ten sediment samples from each of the three basins in Lake Whatcom will be analyzed for methylmercury. These data along with available data on lake chemistry, biology, and circulation patterns will be used to help assess factors that may affect spatial variations in concentrations of mercury in fish and sediment of Lake Whatcom.
Approach for Objective 5
Although it is anticipated that objectives 1 through 4 will be accomplished to a large degree, it is probable that some additional data will be needed identify and characterize sources of mercury in Lake Whatcom. Recommendations for the collection of additional data will be made based on data gaps identified when addressing those objectives.
our apologies; tables not yet formatted
Agency FY2002 FY2003 Total
USGS $26,000 $51,600 $77,600
Whatcom County match USGS $26,900 $51,600 $78,500
Whatcom County to Ecology for sampling & analysis $21,500 $0 $21,500
Total $74,400 $103,200 $177,600
Budget Category FY2002 FY2003
Salaries $41,700 $83,400
Equipment $0 $0
Vehicles $1,300 $2,400
Printing $0 $1,500
Travel $2,400 $0
Supplies $4,000 $0
Report production $0 $15,900
Ecology field time $4,000 $0
Ecology core analyses $17,500 $0
Outside Lab QA $3,500 $0
Total $74,400 $103,200
At the end of the paragraph beginning "Approach for objective 1", add:
"Proposed sampling locations are shown in Figure 1"
At the end of the paragraph headed "Approach for Objective 2", add:
"Proposed coring sites for the three Lake Whatcom cores are shown in Figure 1. Cores to a sediment depth of _____ will be attempted."
Modify Figure 1, to show these sampling locations.
Timelines and Report Products-
The findings of this study will be presented in a USGS Water-Resources Investigations Report and in a technical report published by the Washington State Department of Ecology. The scope of each report has not been determined, but the two reports will compliment, and not duplicate, each other. Intermediate products will include the inventory of data and information and quarterly progress reports by the USGS. The progress reports will include initial findings as they become available and are approved for release.
our apologies; tables not yet formatted
Tasks A M J J A S O N D J F M A M J J A S
Data review X X X X X
Sampling X X X
Data analysis X X X X X X X X X
Draft report X
Final report X
The study will be conducted by geochemist with assistance from hydrologists specializing in water-quality studies.
Original report has two maps
location (we know that), and
Figure 1 Lake Whatcom
|(no significant comments at this time)|